196,407 research outputs found
Reconsidering metaphysical nihilism
No full textIn contemporary analytic philosophy metaphysical nihilism is the thesis
according to which there might be nothing, i.e. a possible world with no concrete
objects in it, but that can contain (or must contain) abstract objects. After summarizing
the set of premises from which analytic metaphysics deals with nothing, I propose a
set of premises that could fit continental metaphysics. Then I propose a new set of
premises for the question of nothing that derives from a synthesis of the two above
mentioned sets. By means of this new set, I try to show that nothing as a possible
world with no objects at all is not a self-contradictory entity and I propose an
argument for proving that an empty possible world exists
Swarm intelligence for hole detection and healing in wireless sensor networks
No full textThe increasing demand for wireless sensor networks to monitor specific regions has prompted extensive research on sustaining coverage over time. The main threat to this goal arises from coverage holes caused by random node deployment or failures. This study proposes a swarm intelligence-based algorithm to detect and heal coverage holes. The swarm of agents relies on local and relative information, activating in response to detected holes and navigating a potential field toward the closest hole. The agents quantize their perceptions to disperse efficiently, approaching holes from different directions to accelerate healing. Based on geometric criteria, the swarm deploys at locally optimal positions along hole borders while preventing redundant deployments. Agents deployment update the potential field, guiding the rest of the swarm toward unhealed areas and ensuring dynamic detection and tracking of new holes, even near the region frontier. Experimental studies demonstrate superior coverage restoration compared to state-of-the-art solutions, showing good scalability and flexibility to different hole sizes, shapes, and multiplicity. Moreover, it exhibits high robustness to the corruption of agents’ perceptions and to their failure, while efficiently managing the battery level
Billet cropping numerical modelling: an approach based on inverse analysis
No full textThe paper presents the development of a numerical model of the slugs shearing process properly calibrated through experimental simulative tests. To this aim a mechanical cropping device was designed and set up; the numerical model of the process was developed considering the previous drawing step to take into account the process chain effect. Compression tests were carried out to determine the material rheological behaviour, while uniaxial tensile tests were devoted to gain workability data to be implemented in the fracture criterion. The accuracy of simulated results is discussed and possible causes of deviation from experimental data underlined and critically assessed
Analysis of cropping operation in cold forging through numerical and experimental techniques
No full textOxygenic photosynthetic responses of cyanobacteria exposed under an M-dwarf starlight simulator: Implications for exoplanet’s habitability
No full textIntroduction: The search for life on distant exoplanets is expected to rely on atmospheric biosignatures detection, such as oxygen of biological origin. However, it is not demonstrated how much oxygenic photosynthesis, which on Earth depends on visible light, could work under spectral conditions simulating exoplanets orbiting the Habitable Zone of M-dwarf stars, which have low light emission in the visible and high light emission in the far-red/near-infrared. By utilizing cyanobacteria, the first organisms to evolve oxygenic photosynthesis on our planet, and a starlight simulator capable of accurately reproducing the emission spectrum of an M-dwarf in the range 350-900 nm, we could answer this question. Methods: We performed experiments with the cyanobacterium Chlorogloeopsis fritschii PCC6912, capable of Far-Red Light Photoacclimation (FaRLiP), which allows the strain to harvest far-red in addition to visible light for photosynthesis, and Synechocystis sp. PCC6803, a species unable to perform this photoacclimation, comparing their responses when exposed to three simulated light spectra: M-dwarf, solar and far-red. We analysed growth and photosynthetic acclimation features in terms of pigment composition and photosystems organization. Finally, we determined the oxygen production of the strains directly exposed to the different spectra. Results: Both cyanobacteria were shown to grow and photosynthesize similarly under M-dwarf and solar light conditions: Synechocystis sp. by utilizing the few photons in the visible, C. fritschii by harvesting both visible and far-red light, activating the FaRLiP response. Discussion: Our results experimentally show that an M-dwarf light spectrum could support a biological oxygen production similar to that in solar light at the tested light intensities, suggesting the possibility to discover such atmospheric biosignatures on those exoplanets if other boundary conditions are met
La testimonianza
No full textThe psychology of witnesses is dealt with in the chapter. after an historical introduction and an exam of the validity of research in this field some main legal concepts related to witnessing activity aare taken into account. Cognitive competence involved in witnessing is then analysed, including recall, interpretativ, and perceptual processes. The testimony itself is then taken into account: legal interview, as well as the verbal and non verbal behavior of witnesses. Finally, the assessment of witness reliability is dealt with
Accurate modelling of the process forming chain to predict cold forged component geometry
No full textBeing in an industrial contest time a key parameter, very often the design of new forging sequences through numerical simulation leads to simplified models which do not allow a correct evaluation of both process and geometric parameters. In the present work, the multi-step cold forging of a small axi-symmetric automotive component, taken as reference case, is investigated. The Authors compare the results obtained by simulating the whole process chain for the component manufacturing with the ones obtained by a more simple numerical model. It turns out how critical it is in terms of results reliability not only the validation of input data but also the correct modelling of the whole process chain
Swarms of Artificial Platelets for Emergent Hole Detection and Healing in Wireless Sensor Networks
No full textMost of the applications of wireless sensor networks require the continuous coverage of a region of interest. The irregular deployment of the nodes, or their failure, could result in holes in the coverage, thus jeopardizing such requirement. Methods to recover the sensing capabilities usually demand the availability of redundant full-fledged nodes, whose relocation should heal the holes. These solutions, however, do not consider the high cost of obtaining redundant, typically complex, devices, nor that they could in turn fail. In this work, we propose a bio-inspired and emergent approach toward hole detection and healing using a swarm of resource-constrained agents with reduced sensing capabilities, whose behavior draws inspiration from the concepts underlying blood coagulation. The swarm follows three rules: Activation, adhesion, and cohesion, adapted from the behavior exhibited by platelets during the human healing process. Relying only on local and relative information, the mobile agents can detect the holes border and place themselves in locally optimal positions to temporarily restore the service. To validate the algorithm, we have developed a distributed, multi-process simulator. Experimental results show that the proposed method efficiently detects and heals the holes, outperforming two state-of-The-Art solutions. It also demonstrates good robustness and flexibility to agent failure
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